warn: detect and report RTK_DISABLED=1 overuse in sessions

[pszymkowiak]

Problem

Claude Code (and other AI agents) may learn to use RTK_DISABLED=1 as a workaround after encountering a single filtering issue, then over-generalize it to all commands — silently killing token savings.

Real example: in a session with 801 Bash commands, 243 (30%) used RTK_DISABLED=1 unnecessarily. This dropped the average savings from ~65-70% to 48.5%. Commands like gh pr list, gh pr view, cargo test, git log, and curl were all bypassed even though RTK handles them correctly.

Root cause

A past bug (#196) where gh --json output was corrupted led to a RTK_DISABLED=1 workaround. The bug was fixed in the rewrite logic (skip --json/--jq/--template), but the workaround persisted in agent memory and spread to unrelated commands.

Proposed solution

1. rtk gain warning: detect RTK_DISABLED=1 usage in tracking DB and warn when >10% of commands bypass RTK
2. rtk discover detection: flag sessions with high RTK_DISABLED=1 usage as "missed savings"
3. Docs: add a note in CLAUDE.md that RTK_DISABLED=1 should almost never be needed (the rewrite hook already skips --json/--jq/--template and unknown commands)

Impact

Could recover 15-20% savings for affected users with zero code change on their side.